One of the examples of a transmission system that transmits and receives content data among a plurality of transmission terminals is a television conference system in which a television conference is held through a communications network such as the Internet. The need for such a television conference system has been increasing because of the recent demand for reduction in cost and time taken for business trips. In such a television conference system, a plurality of television conference terminals, which are examples of the transmission terminals, are used. A television conference can proceed by transmitting and receiving image data and voice data among the television conference terminals.
Recent improvement of the broadband environment enables image data of high image quality and voice data of high sound quality to be transmitted and received. As a result, a state of the other party in a television conference can be easily grasped and communication in conversations can be improved.
When many television conferences are held through a communications network, or when image data and voice data are received by using a narrow bandwidth path on the communications network, a problem arises in that a delay occurs in receiving content data such as the image data and the voice data. It is generally said that users of the television conference system feel stress in conversations if a delay of 0.5 seconds or more occurs in receiving the content data. Because of such stress due to a delay, the users cannot proceed with the television conferences satisfactorily even in the recent improved broadband environment.
In recent television conference systems, a plurality of relaying apparatuses, which relay image data and voice data between the television conference terminals, are installed for each LAN (Local Area Network) in the communications network. The relaying apparatuses decentralize communications processing in a television conference so as to reduce the load of each relaying apparatus, and decentralize the data transmission amount of the content data to be relayed.
Conventionally, when one of the relaying apparatuses is selected and used, the relaying apparatus connected to the LAN to which the television conference terminal used for the television conference is connected is used. That is, the relaying apparatus having an IP address similar to the IP address of the television conference terminal is selected, and high quality content data can be transmitted and received through the selected relaying apparatus (refer to Japanese Patent Application Laid-open No. 2008-227577).
The conventional television conference systems, however, do not always fit the actual environment of the communications network because the relaying apparatus is selected on the assumption that high quality content data could be transmitted and received by using the relaying apparatus having the IP address similar to the IP address of the television conference terminal. Even if the IP addresses of the television conference terminal and the relaying apparatus are preliminarily obtained, it is difficult to grasp the connection conditions of the communications network spreading all over the world. The assumption is not always true due to the presence of disconnections in the actual conditions of the communications network, for example. As a result, a problem arises in that the relaying apparatus that relays high quality content data in the shortest period of time is not always selected under the actual environment of the communications network.